Abstract

Wideband enhancement was implemented by detecting visually relevant edge and bar features in an image to produce a bipolar contour map. The addition of these contours to the original image resulted in increased local contrast of these features and an increase in the spatial bandwidth of the image. Testing with static television images revealed that visually impaired patients (n=35) could distinguish the enhanced images and preferred them over the original images (and degraded images). Most patients preferred a moderate level of wideband enhancement, since they preferred natural-looking images and rejected visible artifacts of the enhancement. Comparison of the enhanced images with the originals revealed that the improvement in the perceived image quality was significant for only 22% of the patients. Possible reasons for the limited increase in perceived image quality are discussed, and improvements are suggested.

References

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Table 1

a The four lower levels were images processed with the Adaptive Enhancement algorithm1
to produce degraded images (K=0.2–0.7).
The fifth level was the original image, and the other ten images were processed with the wideband algorithm with the indicated scale factors (63–3199).

Responders. Subset of Group D who significantly liked the enhanced images

a As not all patients finished all parts of the study, different groups were involved in each comparison; n
is the number of patients in the group. Documented CFL is the number of patients in that group who had central visual field loss. Patients without documented CFL, i.e., without a specific record of scotoma, were considered to have CFL as indicated by their substantially reduced visual acuity and other clinical information.

Table 3

a Categories such as “Text” that had only a small number of images or did not have faces were not included). Face width was the ear-to-ear visual angle computed for the average observation distance of 38 in. For each image the face widths of all faces in that image were first averaged. These average face widths were then averaged to obtain the reported value.

Tables (3)

Table 1

a The four lower levels were images processed with the Adaptive Enhancement algorithm1
to produce degraded images (K=0.2–0.7).
The fifth level was the original image, and the other ten images were processed with the wideband algorithm with the indicated scale factors (63–3199).

Responders. Subset of Group D who significantly liked the enhanced images

a As not all patients finished all parts of the study, different groups were involved in each comparison; n
is the number of patients in the group. Documented CFL is the number of patients in that group who had central visual field loss. Patients without documented CFL, i.e., without a specific record of scotoma, were considered to have CFL as indicated by their substantially reduced visual acuity and other clinical information.

Table 3

a Categories such as “Text” that had only a small number of images or did not have faces were not included). Face width was the ear-to-ear visual angle computed for the average observation distance of 38 in. For each image the face widths of all faces in that image were first averaged. These average face widths were then averaged to obtain the reported value.